如何避免;“线程中的异常”;“主要”;java.util.ConcurrentModificationException“;Java中的错误
我试图计算标准偏差,平均偏差等。我试图写下面的代码。但是它有异常java.util.ConcurrentModificationException。我正在尝试修复它,但失败了 我的代码:如何避免;“线程中的异常”;“主要”;java.util.ConcurrentModificationException“;Java中的错误,java,exception,Java,Exception,我试图计算标准偏差,平均偏差等。我试图写下面的代码。但是它有异常java.util.ConcurrentModificationException。我正在尝试修复它,但失败了 我的代码: package statistic; import java.util.*; public class StanderDeviation { public static void main(String[] args) { System.out.println("step 1:c
package statistic;
import java.util.*;
public class StanderDeviation {
public static void main(String[] args) {
System.out.println("step 1:create a list of 10 numbers :");
List<Double> numbers = new ArrayList<Double>();
numbers.add(23.0);
numbers.add(92.0);
numbers.add(46.0);
numbers.add(55.0);
numbers.add(63.0);
numbers.add(94.0);
numbers.add(77.0);
numbers.add(38.0);
numbers.add(84.0);
numbers.add(26.0);
System.out.println("\n " +numbers);
System.out.println("step 2: average of 10 numbers : ");
double sum = 0;
for(double number : numbers)
{
sum= sum +number;
}
double average = sum / numbers.size();
System.out.println(sum + " / " + numbers.size() + " = " + average);
System.out.println("\nstep 3: difference between each number numbers and average :");
List<Double>listOfDifferences = new ArrayList<Double>();
for(double number : numbers)
{
double difference = number - average ;
listOfDifferences.add(difference);
System.out.printf("%2.2f", difference);
System.out.printf(" ");
}
System.out.println("\n\nstep 4: Square of above calculate difference :");
List<Double> squares = new ArrayList<Double>();
for(double difference : listOfDifferences)
{
double square = difference * difference ;
listOfDifferences.add(difference);
squares.add(square);
System.out.printf("%4.2f", square);
System.out.printf(" ");
}
System.out.println("\nstep 5:sum of Square calculate above :");
sum = 0;
for(double number : squares)
{
sum += number ;
}
System.out.println(sum);
System.out.println();
System.out.println("step 6: divide sum of Square by totle (numbers)-1 :");
double result = sum / (numbers.size()-1);
System.out.printf("%4.2f", result);
System.out.println();
System.out.println("\nstep 7: Stander Deviation is the Square root of obove result :");
double StanderDeviation = Math.sqrt(result);
System.out.printf("%4.2f", StanderDeviation);
}
}
提前感谢。您的问题就在这个循环中:
for(double difference : listOfDifferences)
{
double square = difference * difference ;
listOfDifferences.add(difference);
squares.add(square);
System.out.printf("%4.2f", square);
System.out.printf(" ");
}
您正在尝试将某些内容添加到当前正在迭代的列表中
只需删除差异列表中的行add(差异)代码>
它不会影响标准偏差的计算。(将刚刚从差异列表中收到的差异添加回同一个列表是没有意义的!)您可以创建其他列表
结构(,如果您的情况确实需要它)并向其中添加元素,如:
List<Double> changed = new ArrayList<Double>();
for(double difference : listOfDifferences)
{
double square = difference * difference ;
// listOfDifferences.add(difference);
squares.add(square);
changed.add(difference);
System.out.printf("%4.2f", square);
System.out.printf(" ");
}
List changed=new ArrayList();
for(双重差异:差异列表)
{
双平方=差*差;
//差异列表。添加(差异);
正方形。添加(正方形);
更改。添加(差异);
System.out.printf(“%4.2f”,正方形);
System.out.printf(“”);
}
无法修改您迭代的集合
不要通过添加或删除列表中的项目来修改正在迭代的列表。对不起,我不明白。我是java新手。你能解释一下吗?希望对你有帮助在一个for循环中,比如for(双重差异:差异列表){…}
你不能在差异列表中添加或删除项目。
List<Double> changed = new ArrayList<Double>();
for(double difference : listOfDifferences)
{
double square = difference * difference ;
// listOfDifferences.add(difference);
squares.add(square);
changed.add(difference);
System.out.printf("%4.2f", square);
System.out.printf(" ");
}